Supercharger on my C4
Thread Starter
7th Gear
Joined: Jul 2023
Posts: 7
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From: Pennsylvania
Supercharger on my C4
Hi all, I just joined this forum. I have an '85 C4 that I am planning on supercharging. I've been trying to do a bunch of research however most of it is a few years old and seems outdated. So I am wondering what every-ones suggestions are. I am building the top end as the bottom end has already been built. So I am getting AFR 195 heads, headers, and this is somewhere else that I need a little help. I am not sure what to do for the fuel injection system. I am not sure if I can or how to get rid of the TPI system. This is especially important because I know I need more fuel for the supercharger. Oh I do have a guy with a dyno thats going to tune it when I am done. I am new to this so any suggestions or help is extremely appreciated.
Pro
Joined: Dec 2018
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From: Wisconsin
2023 Corvette of the Year Finalist - Modified
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What's your budget for the EFI system? Don't forget that you'll need a larger fuel pump and injectors to add in that budget.
While the factory EFI system could be made to work, you'll need someone familiar with burning new PROMS (that also has the equipment to do so.) Not many tuners around that fit the bill. You'd be better off using an aftermarket EFI system as most decent tuners can work with the current aftermarket EFI systems.
I built a twin turbocharger system for my 85 a few years ago. I decided to go with a Holley HP for engine management. If I were doing it today I would probably go with the Terminator X as a lower cost option.
By "TPI system" are you referring to the EFI system or the intake manifold? If you're referring to the intake you can go with a Miniram if you're willing to wait (TPIS is swamped and painfully slow to respond/ship) or a SuperRam. I believe there is a SuperRam for sale in the WTS section right now.
While the factory EFI system could be made to work, you'll need someone familiar with burning new PROMS (that also has the equipment to do so.) Not many tuners around that fit the bill. You'd be better off using an aftermarket EFI system as most decent tuners can work with the current aftermarket EFI systems.
I built a twin turbocharger system for my 85 a few years ago. I decided to go with a Holley HP for engine management. If I were doing it today I would probably go with the Terminator X as a lower cost option.
By "TPI system" are you referring to the EFI system or the intake manifold? If you're referring to the intake you can go with a Miniram if you're willing to wait (TPIS is swamped and painfully slow to respond/ship) or a SuperRam. I believe there is a SuperRam for sale in the WTS section right now.
Thread Starter
7th Gear
Joined: Jul 2023
Posts: 7
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From: Pennsylvania
I guess I am not 100% sure. From what I was understanding was that the tuned port injection system on these cars is not the best. I might be wrong though as I mentioned I'm pretty new to this and just trying to learn. I saw the Miniram and was all for it until I saw it was unavailable and I would like to go a different route so I dont have to wait as long. I was thinking about getting rid of the manifold, but if you guys just recommend upgrading the injectors and keeping the system I can do that. Really since Im building it I just want it to be right.
Pro
Joined: Dec 2018
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From: Wisconsin
2023 Corvette of the Year Finalist - Modified
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What intake you use will determine what the rpm range is of the engine along with the camshaft.
Mine has ported and siamesed SLP runners and the horsepower peaks right at 5,200-5,300 rpms. If you're looking for a high revving engine, I would suggest changing your intake. The Miniram does that well. Jim at TPIS has been swamped for a while now so if unless you're willing to wait I would try to find a used one. They do show up occasionally.
What is your target horsepower?
Mine has ported and siamesed SLP runners and the horsepower peaks right at 5,200-5,300 rpms. If you're looking for a high revving engine, I would suggest changing your intake. The Miniram does that well. Jim at TPIS has been swamped for a while now so if unless you're willing to wait I would try to find a used one. They do show up occasionally.
What is your target horsepower?
Melting Slicks
Joined: Apr 2001
Posts: 2,122
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From: Ca.
It sounds like you don't have to deal with smog testing? If not, then it opens up a lot of possibilities. Aftermarket ECM for sure. As for intakes-there is also the stealth ram and super ram. They are lower rpm peak and more torque. They along with the mini ram do show up for sale once in a while, you just have to stay on the look out. So as above what's your goals is the first question to ask. High rpm revver? Or lower peak? That would also have a bearing on your cam choice.
You said you had the short block done-I hope it's all forged and lower compression ratio for boost? Compression ratio would depend on how much boost you'll throw at it. I'm pushing max 14 to 15lbs and down to 7.9:1 to keep it safe on pump gas.
You said you had the short block done-I hope it's all forged and lower compression ratio for boost? Compression ratio would depend on how much boost you'll throw at it. I'm pushing max 14 to 15lbs and down to 7.9:1 to keep it safe on pump gas.
Pro
Joined: Dec 2018
Posts: 734
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From: Wisconsin
2023 Corvette of the Year Finalist - Modified
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Finalist 2020 C4 of the Year - Modified
Ah, almost forgot about a pretty critical question about the bottom end: what's your ring gap? The proper ring gap is dependent upon what power adder you're planning on, if any. Boosted engines need a larger ring gap than an NA one.
Melting Slicks
Joined: Apr 2001
Posts: 2,122
Likes: 224
From: Ca.
Yup, this too!! It really sucks to have your ring ends but together and take off the top of a piston!
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i worry that low of a compression is gonna make it feel like a dog off boost, until get rpms up / start building boost. Esp with a centrifugal supercharger or turbo
D1-SC blower, i ran 12 psi boost, 93 octane, 100% methanol sprayer under boost (no intercooler) and 19-20 degrees timing up top. stock bottom end 1993 lt1 with afr 195 comp elim heads WITH larger -than-stock cc, milled down to produce 9.7:1 static compression ratio
now running 15-16 psi boost on e85, with the meth sprayer still (prob overkill but it was already there), 23 degrees timing up top. Still stock bottom end (it hasnt broke). Also spraying 75 shot nitrous on top of that
Melting Slicks
Joined: Apr 2001
Posts: 2,122
Likes: 224
From: Ca.
that low of a compression un necessary - even for pump gas.
i worry that low of a compression is gonna make it feel like a dog off boost, until get rpms up / start building boost. Esp with a centrifugal supercharger or turbo
D1-SC blower, i ran 12 psi boost, 93 octane, 100% methanol sprayer under boost (no intercooler) and 19-20 degrees timing up top. stock bottom end 1993 lt1 with afr 195 comp elim heads WITH larger -than-stock cc, milled down to produce 9.7:1 static compression ratio
now running 15-16 psi boost on e85, with the meth sprayer still (prob overkill but it was already there), 23 degrees timing up top. Still stock bottom end (it hasnt broke). Also spraying 75 shot nitrous on top of that
i worry that low of a compression is gonna make it feel like a dog off boost, until get rpms up / start building boost. Esp with a centrifugal supercharger or turbo
D1-SC blower, i ran 12 psi boost, 93 octane, 100% methanol sprayer under boost (no intercooler) and 19-20 degrees timing up top. stock bottom end 1993 lt1 with afr 195 comp elim heads WITH larger -than-stock cc, milled down to produce 9.7:1 static compression ratio
now running 15-16 psi boost on e85, with the meth sprayer still (prob overkill but it was already there), 23 degrees timing up top. Still stock bottom end (it hasnt broke). Also spraying 75 shot nitrous on top of that
Last edited by drive it; Jul 4, 2023 at 09:34 PM.
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